Urban Water Supply

Sustainability and resilience in water treatment

In Study Session 4 you read about some factors that can influence the sustainability of a water source. For example, reducing soil erosion by planting trees and retaining vegetation can reduce the amount of silt that accumulates in a reservoir and prolong its life.

For the water treatment process itself to be sustainable (meaning that it can be maintained at its best for a long time) it has to be simple to operate and maintain. Complex systems should be avoided and wherever possible locally available materials should be used. For example, if a coagulant is required, the one that can be purchased in-country will be preferable to one that has to be imported. Water treatment plants consume energy, and if this energy could be supplied through renewable sources (such as solar or wind) it will keep operating costs down and improve sustainability.

The plant and distribution system should be made of robust materials that will have a long operating life. It can be difficult to obtain spare parts, so there should be plans in place for procurement of replacements. (These and other management issues are the subject of the next study session.) Another important factor in sustainability is an effective maintenance system, which needs planning and, importantly, requires well-trained and motivated staff.

Resilience, in the context of a water treatment system, is its ability to withstand stress or a natural hazard without interruption of performance or, if an interruption does occur, to restore operation rapidly. With water treatment plants located very close to water sources, having too much water can be just as much a problem for operations as having too little. Storms and floods, exacerbated by climate change, may overwhelm systems and interrupt operations, so appropriate flood defence measures must be in place. The need to be resilient to these impacts is another reason why the equipment and construction of the plant should be of a high standard.